CSP (``communicating sequential processes'') support for Lisp. This concurrency library makes it easy to organise thread communication in a modular and expressive way. The central primitive is the ``channel'', which acts both as a synchronisation and communication medium. Care has been taken to keep the interface as minimal as possible.

CSP is a translation by Roger Peppe of Plan 9's libthread/channel.c. There are at least two forks that add new features, such as different queue choices, timeouts, and ALT guard conditions: Calispel and ChanL.

The package is layered on top of Bordeaux-Threads for portability. It has had at least rudimentary testing under SBCL, Lispworks, openMCL, ECL and Allegro. Documentation and a couple of examples are included with the package.